Abstract
Cross sections for the elastic electron scattering by HOOCl, HOClO and HClOO isomers are calculated using the R-matrix method. A systematic study considering basis set, polarisation and the Born closure technique is performed. Low-energy resonances are found for both HOOCl and HOClO, near 1.7 and 1.2 eV respectively, but not for HClOO. The lowest-energy resonance for HClOO is observed at 4.5 eV. Basis sets and polarisation effects on the differential cross sections are found to be important for scattering energies below 5 eV for HOOCl and HOClO due to the presence of these resonances. The dependence of the molecular dipole moment on target basis set used affects the integral cross sections (ICS) results. The ICS for HOClO is larger than other two isomers due to its larger dipole moment, around 3.2 D, while the ICS for HOOCl and HClOO have similar magnitude as both their dipole moments are near 1.9 D. Estimated dissociative electron attachment (DEA) cross sections suggest that HOOCl and HOClO will undergo DEA with low-energy electrons but that HClOO requires higher-energy electrons to undergo DEA.
Highlights
Understanding the role played by atmospheric pollutants in the Earth’s atmosphere is important for tackling large scale problems such as climate change and ozone layer depletion
At angles below 30°, the differential cross sections (DCS) of HOOCl and HClOO converge; this forward scattering is dominated by the long-range interactions due to the dipole moment which is taken into account by Born closure and the permanent dipole moments for these isomers are both about 1.9 Debye
The cross sections can be considered reasonably well converged with respect to the number of virtual orbitals used in SE and SEP calculations for all basis sets tested
Summary
Understanding the role played by atmospheric pollutants in the Earth’s atmosphere is important for tackling large scale problems such as climate change and ozone layer depletion. An interesting reaction intermediary proposed in many chain reactions involving chlorine atoms is chlorous acid, HOClO This specie has 2 other isomers: HOOCl and HClOO. This study found that HOOCl is the more stable with an estimated heat of formation of 1.6 kcal mol−1, followed by HOClO and HClOO which heat of formation are 11.9 and 56.2 kcal mol−1, respectively They computed spectroscopic parameters for each isomers which could be used in infrared (IR) spectra to identify them. The HOOCl, HOClO and HClOO isomers are suggested as chlorine reservoirs at the atmosphere and their fragments, according to the authors cited above, participate in intermediary steps in the ozone destruction cycle. In this work we present a theoretical comparative study of gas-phase elastic electron-scattering cross section for the three isomers HOOCl, HOClO and HClOO, calculated using the R-matrix method.
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